With the increasing performance of computers and network communications, demand for high speed and high-density integrated circuits is increasing. Such high performance integrated circuits (“ICs”) tend to require more sophisticated noise filtering techniques such as decoupling capacitors to enhance the reliability of the devices. Decoupling capacitors are typically placed close to power supplies such as Vdd and/or ground. Decoupling capacitors reduce the noise and smooth fluctuations in power supply voltage.
Decoupling capacitors are typically mounted on the printed circuit board (“PCB”) in close proximity to the ICs. As the switching speeds of ICs increase, greater demands are placed on decoupling capacitors. FIG. 1A illustrates a conventional decoupling capacitor 100. Capacitor 100 includes a main body 106 and two end portions 102–104. A typical physical size of a capacitor 100 is a rectangular structure with W (width)×L (length)×H (height), wherein L is typically the longest and H is the shortest in the structure. The two end portions 102–104 provide voltage potentials, also known as +poles/−poles, for capacitor 100. The structure of capacitor 100 is typically referred to as an axial structure. FIG. 1B is a side view 140 of capacitor 100 shown in FIG. 1A in which a capacitor 150 is mounted on a PCB 152. Typically, wires or terminals 162–164 are used to connect capacitor 150 to PCB 152.
Industry has met the demands for greater decoupling capacitors by employing larger and larger capacitors. However, a problem with a conventional capacitor is parasitic inductance. Typically, the larger the capacitor is in size, the larger the parasitic inductance becomes. Parasitic inductance degrades the effectiveness of a capacitor. Capacitors with large parasitic inductance have low resonance frequency making them unusable for many high-speed common applications. For example, it is common to find low power DC/DC or DC-to-DC converters operating at 1 MHz and some even operate at up top 2 MHz. However, high power DC/DC converters are still operating at about 1/10 of the lower power counterparts. One reason is related to the resonance frequency of large capacitors. Large value multilayer ceramic capacitors typically have resonance frequencies of less than 500 kHz versus smaller value multilayer ceramic capacitors with resonance frequencies of greater than 2 MHz. The relationship between resonance frequencies and capacitance can be expressed in the following equation:f=½·(LC)1/2
wherein f represents resonance frequency, L represents parasitic inductance, also known as equivalent series inductance (“ESL”), and C represents capacitance. As can be seen, the smaller the inductance L, the higher the resonance frequency f becomes.
Thus, it would be desirable to have a multilayer capacitor that provides high capacitance with small parasitic inductance.